TH509B - The direct reduction process of iron oxide-containing substances in a rotary furnace. - Google Patents

Abstract

Before iron oxide-containing materials are reduced in a rotary kiln by reacting them with a solid carbon-based reducing agent at a temperature below the melting point of the material, both the iron oxide and the carbon-based reducing agent are preheated in a multiple-hearth kiln. At least some of the reducing agent is either incompletely cokeed or incompletely carbonized at low temperatures to prevent incomplete reduction and ignition. The iron oxide is preheated in the upper part of the multiple-hearth kiln, and the solid carbon-based reducing agent is separately preheated in the lower part. At least the gases obtained from low-temperature carbonization in the lower part of the multiple-hearth kiln are then forced to flow upwards, against the flow of the iron oxide, to heat the upper part as needed.

Claims (4)

1. Direct reduction process of iron oxide-containing substances by reaction with solid carbon reducing zinc at temperatures below the melting point of the substance in a rotary kiln. This involves preheating the iron oxide-containing substance and the carbon reducing zinc in a multiple-hearth kiln before placing them in the rotary kiln. The reducing zinc in the multiple-hearth kiln is then subjected to at least incomplete coke formation or incomplete low-temperature carbonization. A characteristic feature is that the iron oxide-containing substance is preheated in the upper part of the multiple-hearth kiln under conditions of virtually no reduction. The solid carbon reducing zinc is separately preheated in the lower part of the multiple-hearth kiln, and at least some of the low-temperature carbonization gases from the lower part are forced upwards, in an upward motion against the iron oxide-containing substance. 2. The process under Requisition I, in which the low-temperature carbonizing gases flow into the upper part of the multiple-hearth furnace and are at least partially combusted during the process before or while entering the upper part of the multiple-hearth furnace. 3. The process under claim 2 in which at least the majority of the volatile and combustible components of the gases obtained from low-temperature carbonization are burned before or while such gases enter the upper part of the multiple-hearth furnace. 4. The process under Requisition I, in which the outlet temperature of the gases from the top of the multiple-hearth furnace is maintained above the combustion point temperature of the gases and the combustion of the combustible residue is achieved by supplying air.